U.S. patent application number 13/784072 was filed with the patent office on 2013-10-03 for medical balloon with incorporated fibers.
This patent application is currently assigned to Cook Medical Technologies LLC. The applicant listed for this patent is COOK MEDICAL TECHNOLOGIES LLC. Invention is credited to Steen Aggerholm, Tue Bodewadt, Thomas Lysgaard.
Application Number | 20130261546 13/784072 |
Document ID | / |
Family ID | 46087190 |
Filed Date | 2013-10-03 |
United States Patent
Application |
20130261546 |
Kind Code |
A1 |
Aggerholm; Steen ; et
al. |
October 3, 2013 |
MEDICAL BALLOON WITH INCORPORATED FIBERS
Abstract
A balloon catheter assembly comprises a balloon having attached
to or in its wall one or more filar elements, extending from one
end of the balloon to the other. The filar elements are made of a
material which is at least as flexible as the material forming the
walls of the balloon. In the event of circular burst of the
balloon, the filar element(s) prevent disconnection of the material
of the balloon into two or more separate pieces. The filar
element(s) become attached to or in the material of the balloon
wall when the raw material is inflated to the shape of a mold. The
filar elements may comprise a natural fiber, a synthetic fiber or a
metal wire.
Inventors: |
Aggerholm; Steen; (St.
Heddinge, DK) ; Bodewadt; Tue; (Herfoelge, DK)
; Lysgaard; Thomas; (Solroed Strand, DK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
COOK MEDICAL TECHNOLOGIES LLC |
Bloomington |
IN |
US |
|
|
Assignee: |
Cook Medical Technologies
LLC
Bloomington
IN
|
Family ID: |
46087190 |
Appl. No.: |
13/784072 |
Filed: |
March 4, 2013 |
Current U.S.
Class: |
604/103.06 ;
264/535 |
Current CPC
Class: |
A61M 25/1002 20130101;
B29D 22/02 20130101; A61M 2025/1084 20130101; A61M 25/104 20130101;
A61M 25/10 20130101; A61M 25/1029 20130101; A61M 2025/1031
20130101; A61M 2025/1075 20130101; B29L 2031/7543 20130101; B29C
2049/0089 20130101; B29C 49/48 20130101 |
Class at
Publication: |
604/103.06 ;
264/535 |
International
Class: |
A61M 25/10 20060101
A61M025/10 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 27, 2012 |
GB |
1205362.5 |
Claims
1. A balloon catheter assembly including: a catheter; an inflatable
balloon having a longitudinal direction and comprising a balloon
wall made from at least one balloon material and provided with a
body portion, first and second end cones, and first and second neck
portions, which neck portions are attached to the catheter; and one
or more filar elements formed of at least one filar material
attached to or embedded in the balloon wall, wherein the one or
more filar elements extend solely in the longitudinal direction of
the balloon from the first neck portion to the second neck portion;
wherein the one or more filar elements provide a barrier to
circumferential tear propagation.
2. An assembly according to claim 1, wherein the one or more filar
elements are at least as flexible as the balloon wall.
3. An assembly according to claim 1, wherein the one or more filar
elements provide no material scoring or abrading function.
4. An assembly according to claim 1, wherein the filar elements are
at least as flexible as the balloon wall at least in a longitudinal
direction of the balloon.
5. An assembly according to claim 1, wherein the filar element or
elements are compressible.
6. An assembly according to claim 1, wherein the balloon wall has a
thickness of between about 0.005 millimeters and about 0.080
millimeters.
7. An assembly according to claim 1, wherein the at least one filar
element has a diameter of between around 0.01 millimeters and 0.05
millimeters.
8. An assembly according to claim 1, wherein the at least one filar
element has a linear density (dtex) of between 10 and 60.
9. An assembly according to claim 1, wherein the at least one filar
element is multi-filamentary, each having from around 5 to 50
strands per element.
10. An assembly according to claim 9, wherein the at least one
filar element has around 25 strands.
11. An assembly according to claim 9, wherein each strand has a
density of around 0.5 to 2 denier.
12. An assembly according to claim 1, wherein the at least one
filar element has a tensile strength of between around 4N to around
20N.
13. An assembly according to claim 1, wherein the at least one
filar element exhibits an elongation at break of no more than
around 5%.
14. An assembly according to claim 1, wherein the at least one
filar element is at least one of: completely embedded in the
balloon wall and partially embedded in the balloon wall.
15. An assembly according to claim 1, wherein the at least one
filar material comprises natural and/or synthetic fiber.
16. An assembly according to claim 15, wherein the at least one
filar material comprises as least one of: para-aramid synthetic
fiber, ultra high molecular weight polyethylene,
polytetrafluoroethylene fiber, carbon fiber, cotton and the
like.
17. An assembly according to claim 1, wherein the balloon wall
comprises an outer layer of a first material and an inner layer of
a second material, wherein a softening or melting temperature of
the first material is lower than a softening or melting temperature
of the second material.
18. A method of forming a balloon for a balloon catheter, including
the steps of: providing a mold; providing one or more filar
elements along the entire length of the mold; heating a balloon
material in the mold; and inflating the balloon material to the
shape of the mold to form the balloon, said balloon having a
longitudinal direction; wherein the heating and inflating steps
attach or embed the one or more filar elements on or in the balloon
wall with the one or more elements extending solely in the
longitudinal direction of the balloon.
19. A method according to claim 18, wherein the balloon material is
formed by co-extruding raw material to form a balloon wall
comprising an outer layer of a first material and an inner layer of
a second material, wherein a softening or melting temperature of
the first material is lower than a softening or melting temperature
of the second material.
20. A method according to claim 19, wherein the heating and
inflating steps completely embed the at least one filar element in
the balloon wall.
Description
CROSS-REFERENCE RELATED APPLICATIONS
[0001] This application claims priority to GB application no.
1205362.5, filed Mar. 27, 2012, titled "Medical Balloon with
Incorporated Fibers," the contents of which are incorporated herein
by reference.
TECHNICAL FIELD
[0002] The present invention relates generally to medical devices
and more particularly to a balloon of a balloon catheter. The
teachings herein can be used in balloons used for numerous medical
applications, including for example angioplasty, scoring or
cutting, occlusion, valvuloplasty, to expand implantable medical
devices and so on.
BACKGROUND ART
[0003] Balloon catheters, which generally comprise a catheter tube
with an inflatable balloon at the distal end thereof, are widely
used in the medical profession for various endoluminal procedures.
One common procedure involving the use of a balloon catheter
relates to angioplasty dilation of coronary or other arteries
suffering from stenosis (that is, a narrowing of the arterial lumen
which restricts blood flow). Other procedures of the types
mentioned above are also practiced in the art.
[0004] In all balloon catheter procedures there is a risk that the
balloon may burst, either during its inflation or during the
medical procedure itself. When balloon burst occurs, only parts of
the balloon which remain attached to the catheter are easily
recoverable from the site of the procedure by the withdrawal of the
catheter. Thus, if the balloon bursts in such a way that all the
balloon material remains connected in a single piece, and therefore
attached to the catheter, then all of the material of the burst
balloon is recoverable by withdrawal of the catheter. On the other
hand, if the balloon bursts in such a way that the balloon material
becomes circumferentially disconnected into two or more separate
fragments or pieces, that is suffers a circumferential burst, only
fragments or sections of the balloon material which remain attached
to the catheter are recoverable by withdrawal of the catheter.
Fragments of the balloon which become disconnected from the
catheter are not so easily recovered and can require a separate
medical procedure to remove them.
[0005] Current methods to address the problems resulting from
circumferential burst of medical balloons include increasing the
thickness of the material used to form the balloon walls and
providing complex balloon structures with strengthening sleeves,
braiding or meshes. While these approaches may reduce the chance of
balloon burst, they are far from ideal solutions. For example,
thickening the balloon walls or introducing additional
strengthening elements may reduce the flexibility and
compressibility of the balloon, leading to an increase in the
balloon and introducer profile. This is contrary to the general
desire for as small a balloon and introducer profile as
possible.
DISCLOSURE OF THE INVENTION
[0006] The present invention seeks to provide an improved medical
balloon and balloon catheter assembly.
[0007] According to an aspect of the present invention, there is
provided a balloon catheter assembly including: a catheter; an
inflatable balloon having a longitudinal direction and comprising a
balloon wall made from at least one balloon material and provided
with a body portion, first and second end cones, and first and
second neck portions, which neck portions are attached to the
catheter; and one or more filar elements formed of at least one
filar material attached to or embedded in the balloon wall, wherein
the one or more filar elements extend solely in the longitudinal
direction of the balloon from the first neck portion to the second
neck portion; wherein the one or more filar elements provide a
barrier to circumferential tear propagation.
[0008] The filar elements provide circumferential strengthening of
the balloon along its entire unsupported length, that is along the
entire length of the balloon which is not fixed to and thus
supported by the catheter. They provide a barrier to stop the
propagation of a circumferentially extending tear in the balloon,
thereby no prevent or substantially reduce the risk of the balloon
tearing into separate and loose components. More specifically, an
advantage of this structure is that if a circumferential balloon
burst develops, the filar element or elements halt the
circumferential propagation of the tear, thus ensuring that the
balloon material remains connected in a single piece and remains
attached to the catheter. In this way, the entire balloon is
readily recoverable from the site of the procedure by withdrawal of
the catheter, even after the event of a circumferential burst.
[0009] The filar elements extend solely along the longitudinal
direction of the balloon, that is there are no filar elements which
extend circumferentially around the balloon in annular manner. This
allows the balloon to expand radially outwardly without any
material constraint from the filar elements. That is to say, there
are no filar elements which extend circumferentially around the
balloon, in ring or similar format.
[0010] In the preferred embodiment, the filar element or elements
do not materially affect the flexibility of the balloon. In
practice, the filar elements may be as flexible as the balloon wall
at least in a longitudinal direction of the balloon. This leads to
a structure in which circumferential propagation of a tear in the
balloon wall is halted, without any compromise in the ability of
the balloon to expand radially outwards, and without the need for
an overly complex balloon structure or thickened balloon wall.
[0011] The filar elements thus do not materially or measurably
alter the performance of the balloon in terms of the functions
intended to be performed by the balloon. They exist solely to
prevent complications should the balloon burst. In particular, the
filar elements have no scoring or abrading effect on a vessel
wall.
[0012] In an embodiment, the filar element or elements are
compressible, that is in a direction transverse to the
longitudinal. Such compressibility minimizes the chance of the
filar elements affecting the performance of the balloon,
particularly in the case where they are positioned on the surface
of the balloon wall or only partially embedded therewith.
[0013] Preferably, the balloon wall has a thickness of between
about 0.005 millimeters and about 0.080 millimeters and,
advantageously, the at least one filar element has a diameter of
between around 0.01 millimeters and 0.05 millimeters.
[0014] The at least one filar element may be completely embedded in
the balloon wall, partially embedded in the balloon wall or may
even be positioned on the balloon wall, either on the outside of
the balloon or on the inside thereof.
[0015] The filar element or elements may be single strand
structures or may be multi stranded. Advantageously, the at least
one filar material comprises natural and/or synthetic fiber. The
material may, for instance, comprise as least one of: para-aramid
synthetic fiber such as Kevlar, ultra high molecular weight
polyethylene such as Dyneema, polytetrafluoroethylene fiber such as
Gore-Tex, carbon fiber, cotton and the like.
[0016] In a practical embodiment, the filar elements have a linear
density (dtex) of between 10 and 60 and are multi filamentary, each
having from around 5 to 50 filaments per strand, preferably around
25 filaments. Each filament may have a density of around 0.5 to 2
denier (or similar dtex density).
[0017] The filar elements preferably have a tensile strength of
between around 4N to around 20N. They may have an elongation at
break of no more than around 5%.
[0018] The filar element(s) are made of a material resistive to
breakage and tear and which is preferably significantly stronger
than the balloon wall, thereby being strong enough to halt
circumferential propagation of a tear in the balloon wall.
[0019] In an embodiment, the balloon wall comprises an outer layer
of a first material and an inner layer of a second material,
wherein a softening or melting temperature of the first material is
lower than a softening or melting temperature of the second
material.
[0020] The filar element or elements are preferably at least
partially embedded in the outer layer of the balloon wall.
[0021] The filar element or elements preferably extend
longitudinally, that is along the longitudinal axis of the balloon,
but may extend at an angle to the longitudinal, such as helically.
The filar element or elements preferably do not extend transversely
around the circumference of the balloon in annular manner.
[0022] The size and flexibility of the filar element(s) is
advantageously such that the properties of the balloon, for example
its ability to be wrapped onto the catheter, its wall thickness and
its flexibility, are not materially affected by the provision of
the filar element(s) on or in the balloon wall. This is
particularly important when the balloon is for use in more delicate
applications, such as in smaller and more delicate vessels
including for instance cerebral vessels, where the overall
thickness of the balloon catheter, when the balloon is wrapped onto
the catheter for endoluminal delivery, may be of the order of 1 mm
or less.
[0023] The filar elements are such that they do not cause
interference with or damage to the interior surface of the lumen at
the site to which the balloon is deployed. In this regard, the
filar elements may be completely embedded in the balloon wall or
produce only a minor protrusion which does not cut or score into
the vessel wall. The flexibility of the filar elements will also
ensure that these do not cut or score the vessel wall.
[0024] According to another aspect of the present invention, there
is provided a method of forming a balloon for a balloon catheter,
including the steps of: providing a mold; providing one or more
filar elements along the entire length of the mold; heating a
balloon material in the mold; and inflating the balloon material to
the shape of the mold to form the balloon, said balloon having a
longitudinal direction; wherein the heating and inflating steps
attach or embed the one or more filar elements on or in the balloon
wall with the one or more elements extending solely in the
longitudinal direction of the balloon.
[0025] Advantageously, the balloon material is formed by
co-extruding raw material to form a balloon wall comprising an
outer layer of a first material and an inner layer of a second
material, wherein a softening or melting temperature of the first
material is lower than a softening or melting temperature of the
second material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Embodiments of the present invention are described below, by
way of example only, with reference to the accompanying drawings,
in which:
[0027] FIG. 1 shows a schematic view of an embodiment of balloon
catheter introducer assembly;
[0028] FIG. 2 is an enlarged cross-sectional view of the distal end
of a balloon catheter of FIG. 1;
[0029] FIG. 3 is a side elevational view of a balloon structure in
accordance with an embodiment of the present invention;
[0030] FIG. 4 is a schematic representation showing example
positions of the fibers with respect to the balloon wall;
[0031] FIG. 5 is an exploded view of a mold in accordance with an
embodiment of the present invention;
[0032] FIG. 6 is a cross-sectional view along line IV-IV of FIG. 5;
and
[0033] FIG. 7 shows a cross-section of a part of a balloon 44 in
the process of manufacture.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] It is to be understood that the drawings do not show the
various elements of the device to scale and often these are shown
in enlarged form, solely for the purposes of clarity of
explanation.
[0035] Referring first to FIG. 1, there is shown an embodiment of
introducer apparatus 10 which is deployed endoluminally in a
patient and includes a catheter 12 on which a medical balloon 18 is
fitted. The structures of the preferred embodiments of balloon are
described in further detail below. The combination of catheter 12
and balloon 18 is typically termed a balloon catheter.
[0036] At a proximal end of the catheter 12 there is provided an
external manipulation and valving unit 20. The unit 20 can be of
conventional form and is therefore not described in detail herein
as its components and structure will be readily apparent to the
skilled person. Typically, the unit will include one or more ports
30, 32 for the supply or removal of fluid from the components of
the apparatus 10, such as inflation fluid for the balloon 18 and
flushing fluid into the assembly.
[0037] The balloon 18 is typically fitted into the introducer
apparatus 10 in a deflated and wrapped condition, in which it has a
small diameter, and is covered by a sheath (not shown). Upon
location of the distal end of the assembly 10 at the site to be
treated, the sheath is retracted to expose the balloon 18 and then
the balloon 18 is inflated so as to adopt the shape shown for
example in FIGS. 2 and 3.
[0038] FIG. 2 shows an enlarged view of a typical balloon catheter
and balloon 18 in longitudinal cross section. The balloon 18
normally has a generally circular cylindrical form and is secured
at its ends to the catheter 12. The balloon 18 may be made of a
thermoformable, substantially non-compliant material such as
polyether block amide (such as Pebax), polyamide (such as Nylon
12), polyethylene, PET or polyurethane. The balloon may be formed
from a co extrusion of different layers or blend of more than one
of these materials.
[0039] As used herein, the term thermoformable refers in general to
a material that may be shaped under conditions of temperature
and/or pressure. Preferably, the thermoformable polymer is
stretchable or formable, in some instances flowable, above a
certain processing temperature, but takes a set form having desired
resilience and strength properties at a temperature of intended use
(such as room temperature to body temperature).
[0040] The balloon 18 is inflatable and thus impermeable or
substantially impermeable, as well as being capable of being
wrapped or folded to a relatively small diameter for endoluminal
delivery.
[0041] When the balloon 18 is used to deploy a medical device, in
practice the medical device is fitted over the balloon 18 when the
latter is in a deflated and wrapped configuration on the catheter
12, in known manner.
[0042] In this embodiment, the balloon 18 has a substantially
cylindrical body portion 34 and first and second end cones 36, 38
each bounded by a respective neck portion 40, 42. The portions 34
to 42 of the balloon 18 are typically formed by heating and
inflation of a raw tubing in a suitable mold, as is described in
more detail below. This heating and inflation forms the end cones
36, 38 as well as the body portion 34. Neck portions 40, 42 may be
the unstretched raw tubing but may also be formed by radially
compressing the end portions of the raw tubing during the heating
and inflation process.
[0043] The balloon 18 is fixed or bonded to the catheter 12 at the
neck portions 40, 42 of the balloon 18.
[0044] In general, it is preferred that the balloon 18 has
relatively thin walls, as wall thickness affects the size
(diameter) of the balloon when folded or wrapped as well as its
flexibility. However, it is typical of prior art balloons that the
end cones 36, 38 have walls which are thicker than the walls of the
body portion 34 as a result of the balloon forming process.
Specifically, the end cone portions 36, 38 will typically have a
wall thickness which increases in the direction of narrowing of the
taper, as a result of the lesser amount by which these portions
expand during formation of the balloons.
[0045] FIG. 3 shows a balloon 44 in accordance with an embodiment
of the present invention. As with the balloon 18 shown in FIG. 2,
the balloon 44 has in this example a cylindrical body portion 34
and first and second end cones 36, 38 each bounded by a respective
neck portion 40, 42.
[0046] The wall of the balloon 44 may be a single layer or of a
plurality of layers, preferably two layers of material which are
coextruded and integral with one another. In the case that the
balloon has two or more layers, the outer layer may be of a
material having a softening or melting temperature which is lower
than the softening or melting temperature of the material of the
inner, underlying, layer. The wall of the balloon 44 could equally
be formed of three of more layers. It is to be understood that the
outer layer could be formed of a material which becomes more
flowable than the inner layer of the balloon at the production
temperatures used.
[0047] The thickness of the balloon wall is preferably between
around 0.005 millimeters to around 0.08 millimeters, typically for
a balloon having an inflated diameter of around 1.5 millimeters to
around 36 millimeters.
[0048] The balloon 44 contains one of more filar elements 46, which
are attached to or incorporated in the outer layer of the balloon
structure 44. The purpose of the filar elements 46 is to halt the
circumferential propagation of a tear in the balloon wall. These
filar elements are strong but are thin and/or flexible so as not to
affect adversely the properties of the balloon, in particular
balloon flexibility and wrappability.
[0049] The balloon 44 of FIG. 3 has four sets of filar elements 46
extending along the length of the balloon, only two being visible
in the view of FIG. 3. It is to be understood, though, that a
different number of filar elements 46 may be used and in some
instances there may be just a single filar element 46, while in
other embodiments there may be two, three or more than four.
[0050] The filar elements 46 may be at least as flexible as the
balloon wall and in some instances may be more flexible than the
balloon wall. More particularly, the filar elements 46 may be at
least as flexible as the balloon wall at least in a longitudinal
direction of the balloon. In particular, the filar elements 46 are
not intended to affect the normal characteristics or properties of
the balloon 44, allowing the balloon to perform in the same manner
as a balloon of similar structure but with no filar elements,
especially to provide no scraping or scoring effect whatsoever to
the balloon. In the preferred embodiment, the filar elements are
compressible in a direction transverse to their length, having a
hardness of no more than a hardness of the balloon wall, preferably
less than that of the balloon wall.
[0051] Thus, in the preferred embodiment, the filar elements 46 do
not materially affect the flexibility of the balloon. In practice,
the filar elements 46 may be as flexible as the balloon wall at
least in a longitudinal direction of the balloon. This leads to a
structure in which circumferential propagation of a tear in the
balloon wall is halted, without any compromise in the ability of
the balloon to expand radially outwards, and without the need for
an overly complex balloon structure or thickened balloon wall.
[0052] The at least one filar element 46 advantageously has a
diameter of between around 0.01 millimeters and 0.05
millimeters.
[0053] The filar elements are formed of a material which is
different from the material or materials of the balloon wall and
could be formed as a single strand of material but in preferred
embodiments are formed as a multi-stranded material. They may be
made of natural or synthetic fiber or a combination of the two.
Suitable materials include para-aramid synthetic fiber such as
Kevlar, ultra high molecular weight polyethylene such as Dyneema,
polytetrafluoroethylene fiber such as Gore- Tex, carbon fiber,
cotton and the like. It is to be understood that the filar elements
46 may be made of a plurality or mix of these filar materials.
[0054] In the preferred embodiment, the filar elements have a
linear density (dtex) of between 10 and 60 and are multi
filamentary, each having from around 5 to 50 strands per element,
most preferably around 25 strands. Each strand of the multi
filament element may have a density of around 0.5 to 2 denier (or
similar dtex density). The use of multi-filament elements provides
a number of advantages. First, the elements are compressible in
bulk, primarily by allowing sliding of the fibers or strands over
one another, which results in increased compressibility. Secondly,
the fibers can be made of a material of high tensile strength
compared to the balloon yet without adversely affecting the
longitudinal flexibility of the balloon. Thirdly, the multi
stranded filaments can minimize, particularly avoid, any surface
differences or performance differences to the balloon compared to
an equivalent balloon without such filar elements. Fourthly, these
features allow for the use of materials which are significantly
stronger than the balloon without affecting the performance
characteristics of the balloon. Other advantages will become
apparent to the skilled person.
[0055] The filar elements preferably have a tensile strength of
between around 4N to around 20N. They may have an elongation at
break of no more than around 5%. In other words, the filar elements
have a substantial tensile strength with little elongation prior to
breakage, which optimizes their qualities for stopping tear
propagation.
[0056] Each filar element 46 extends longitudinally between the two
ends of the balloon 44, preferably substantially parallel to the
longitudinal axis of the balloon structure 44. The filar elements
46 extend through the end cones 36, 38 and neck portions 40, 42,
and extend all the way to the distal and proximal ends of the
balloon 44. As such, the filar elements 46 act as strengthening
elements for interconnecting the entire length of the balloon 44,
that is to say filar elements 46 serve to connect both ends of the
balloon 44 in a continuous manner such that all points along the
length of the balloon 44 are attached to the filar element 46 at
some location around the circumference of the balloon 44. In the
preferred embodiment there are no filar elements 46 which extend
circumferentially around the balloon 44, that is as annular rings
around the balloon.
[0057] In the embodiment shown in FIG. 3, the filar elements 46
extend through the conical end portions and through the necks to
the extremities of the balloon, that is for the entire extent of
the balloon 44. It is not essential that the filar elements 46
extend all the way to the very extremities of the balloon. It is,
however, important that the fibers extend from the body portion
past the point where the balloon is fixed or bonded to the catheter
and terminate in the region in which the balloon is fixed or bonded
to the catheter. In the arrangement of FIG. 3, this means that the
filar elements 46 may extend from the body portion 34 past the
point where the end cones 36, 38 join the respective neck portions
40, 42, and terminate in the regions of the two neck portions 40,
42 but before the very ends of the balloon. For the sake of ease of
manufacture, though, t is preferred that the filar elements extend
for the entire length of the balloon.
[0058] The filar elements 46 are preferably embedded in the balloon
material, advantageously in an outer layer of the balloon. Various
examples of the position of the filar elements 46 with respect to a
balloon wall 50 are shown in FIG. 4. It is to be appreciated that
in an embodiment the balloon has two layers and thus that FIG. 4
shows only the outer layer. In position "A", the filar elements 46
are completely embedded in the outer layer of the balloon wall 50,
such that there is no protrusion from the outer surface 52 of the
balloon. In position "B", the filar elements 46 are again
completely embedded in the balloon wall 50 such that there is no
protrusion from the outer surface 52 of the balloon, although the
filar elements 46 are located proximate the outer surface 52 of the
balloon. In position "C", the filar elements 46 are partially
embedded in the balloon wall 50 such that a portion of each fiber
46 protrudes from the outer surface 52 of the balloon. In position
"D", the filar elements 46 are partially embedded in the balloon
wall 50 such that a portion of each filar elements 46 protrudes
from the outer surface 52 of the balloon. The protruding portion of
the filar elements 46 is greater in position "D" than in position
"C". The filar elements 46 may even be positioned on the surface of
the balloon 44, either on the outer surface or on the inner
surface.
[0059] In the examples in which the filar elements protrude from
the outer surface of the balloon, either the degree of this
protrusion is small enough, or the filar elements are flexible
enough, that their presence does not affect the function of the
balloon. In the preferred embodiments, the filar elements have no
noticeable or measurable effect on the characteristics of the
balloon 44.
[0060] The materials of the filar elements 46, such as those
disclosed herein, has a high tensile strength to as not to rupture
should the balloon wall tear. Yet, they are sufficiently flexible
not to materially affect the flexibility of the balloon. Moreover,
by being attached to or embedded in the balloon wall, the filar
elements 46 will wrap with the balloon for delivery and subsequent
deployment. The nature of the filar elements will have no effect on
the wrappability of the balloon.
[0061] The raw tubing used for the manufacture of the balloons
taught herein is advantageously a continuous length of tubing
having a substantially circular cylindrical tube portion.
[0062] FIGS. 5 and 6 show an embodiment of apparatus used to mold
such raw tubing into the required balloon form. As can be seen in
FIG. 5, the mold 60 comprises a central body section 62 and two end
caps 64, 66. The central body section 62 forms the body portion of
the balloon, and the end caps 64, 66 form the respective end cones
of the balloon. The end caps 64, 66, which may themselves be in a
plurality of parts which can be disassembled, that is can be
removed from the central section 62 for removal of the formed
balloon from within the mold 60.
[0063] Prior to molding, one or more filar elements 46 are located
through the mold 60, extending beyond the end caps 64, 66 of the
mold 60. The raw tubing is fed into the mold from an end port and
then inflated in the mold 60 under heat so as to stretch the
central part of the raw tubing to form the body portion and end
cones of the balloon, while the ends of the raw tubing are held
radially compressed so as not to inflate, thus forming the neck
portions of the balloon. After the balloon has been formed in this
way, the balloon is cooled and then removed from the mold.
[0064] The inflation of raw tubing 70 in the mold 60 is shown
diagrammatically in FIG. 6. The raw tubing 70 expands in the
direction of the arrows 72 towards the inner surface of the mold
60, in so doing pushing the filar elements 46 towards the inner
surface of the mold. When the raw tubing 70 is fully expanded with
the filar elements 46 unable to move further, being bounded by the
mold wall, they become at least partially embedded into the outer
layer of the balloon, which will have been heated at least to a
softening or flowing temperature.
[0065] As described above, the preferred embodiment has a balloon
formed of two layers, with the inner layer becoming less flowable
than the outer layer during the balloon formation process. The
filar elements 46 will therefore become embedded in the outer layer
but not the inner layer of the balloon.
[0066] Subsequent cooling of the mold will cause cooling and then
setting of the balloon, which can then be removed with the filar
elements attached.
[0067] In FIG. 5 four filar elements 46 are located in the mold,
and thus four filar elements 46 will extend generally linearly
along the outer surface of the balloon. In practice, however, there
may be provided a different number of filar elements 46 such as
one, two, three or more than four.
[0068] Referring to FIG. 7, there is shown a cross-sectional
schematic view of an example of mold with a balloon in the process
of being formed. The mold has a mold wall 60 which supports the raw
tubing on inflation, to the shape of the final balloon 44. In this
embodiment the balloon 44 is formed of two layers, an outer layer
80 of a reflow material, or material with a lower softening
temperature, and an inner layer 82 of a material having a higher
softening temperature. The filar element 46 becomes embedded in the
balloon, specifically within the outer layer 80. The inner layer 82
acts as a support layer, not only to the filar elements 46 but also
to the outer player 80. Even though in the mild, the thickness of
the filar elements 46 may cause the inner layer 82 to curve
slightly around the filar elements 46, this will not be exhibited
during later use of the balloon 44. As explained above, the filar
elements 46 are flexible enough, and in some cases at least
compressible enough, not to have any material effect on the
characteristics or performance of the balloon 44.
[0069] In another embodiment, the balloon may be formed as a single
layer, in which case the filar elements 46 will become embedded in
the single layer of the balloon wall.
[0070] Other elements could be incorporated into the balloon
structure in addition to the filar elements, depending on the
intended purpose of the resulting balloon catheter. For example,
one or more scoring elements could be disposed on the balloon.
[0071] Although the filar elements have been described as extending
substantially linearly along the longitudinal direction of the
balloon, this is not essential. They could extend at an angle
thereto. They could, for example, wind around the balloon in a
helical manner.
[0072] All optional and preferred features and modifications of the
described embodiments and dependent claims are usable in all
aspects of the invention taught herein. Furthermore, the individual
features of the dependent claims, as well as all optional and
preferred features and modifications of the described embodiments
are combinable and interchangeable with one another.
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